The first major national poll taken since Sen. Barack Obama's speech on race in America shows Obama and Sen. Hillary Rodham Clinton in a virtual tie, reversing Obama's slide in the polls after the wide airing of controversial remarks made by his pastor, the Rev. Jeremiah Wright.

"It's hard to disentangle the impact of (Obama's) speech," Gallup Poll Editor in Chief Frank Newport said Tuesday. The latest Gallup Poll, taken March 22, showed the Illinois senator with 47 percent of the national Democratic vote and Clinton with 46. On March 18 - the day of Obama's speech - after clips of Wright's sermons had permeated the media, Clinton held a seven-point lead over Obama.

Said Newport: "All we know is that he made a speech, and a couple of days later, he was tied with Hillary when a couple days before he was down seven points. It's not insignificant."

Obama's much-praised speech called on Americans to break the racial stalemate that has long divided the country, frankly addressing the prejudices and fears of both blacks and whites. But critics said Obama should have criticized his pastor and mentor more forcefully instead of saying he could no more disown Wright for his remarks than he could his own white grandmother.

Hard to predict

While this week's Gallup Poll is among the first qualitative signs that Obama's address may have been a political success, it is hard to predict the long-term impact of a hot-button speech that's delivered in the short-attention span theater of a presidential campaign. So much of the success depends on factors far beyond the sound of a politician's voice, no matter how eloquent.

More than anything else, the culture has to be primed to embrace the change that a politician is describing, said David Hollinger, a professor of history at UC Berkeley. "You don't do these speeches in a vacuum."

While John F. Kennedy's 1960 speech distancing his Catholicism from how he'd be president is now viewed as a cultural milestone, Sen. Thomas Eagleton's attempts to downplay his mental illness treatment after being selected as the Democratic vice presidential nominee in 1972 failed.

Polls aside, on Tuesday, the Clinton campaign showed it will test the power of Obama's speech as the New York senator addressed the Wright controversy for the first time.

When asked at a Greensburg, Pa., campaign stop if Obama should have left Wright's church, Clinton said, "I think that given all we have heard and seen, he would not have been my pastor." Reading her response largely from notes, Clinton said, "We don't have a choice when it comes to our relatives. We have a choice when it comes to our pastors and the churches we attend."

Trying to address hot-button topics like religion, race and mental illness in a political campaign is frequently combustible.

Kennedy's Catholic issue

When Kennedy addressed a Protestant ministers' convention in Houston in September 1960, his words sounded weary, almost defensive, of having to address the "Catholic issue."

"So it is apparently necessary for me to state once again - not what kind of church I believe in, for that should be important only to me - but what kind of America I believe in," Kennedy told the ministers. Later, he added, "Today I may be the victim, but tomorrow it may be you - until the whole fabric of our harmonious society is ripped apart at a time of great national peril."

What maximized the impact of the speech, Hollinger said, was that the previous year, Pope John XXIII had announced his intention to convene the Vatican II conference, which was designed to modernize the church and broaden its communication with the world.

So Kennedy's pointed speech outlining the kind of America in which he believed was successful in the context of a changing Catholic church, Hollinger said. A Gallup poll taken in October 1960 asked, "As you know, Sen. Kennedy is a Catholic. Has this fact made you more in favor of him, less in favor of him, or hasn't it made any difference at all?" The survey found that 73 percent of the respondents found it made no difference at all. The next month, the Democrat was elected president.

While Kennedy's speech helped propel him to the White House, former GOP Mass. Gov. Mitt Romney didn't gain any ground in December after he sought to defang concerns about how his Mormon faith would inform his politics.

Romney's Mormonism

Kennedy mentioned Catholicism by name several times in his speech, but Romney used the word "Mormon" only once, preferring to use the more generic phrases "my church" or "my faith."

That lack of a personal touch, combined with the dearth of any pro-Mormon groundswell in the culture may have doomed the speech's impact, analysts said.

"The tendency for politicians, when dealing with race and religion, is to just steer clear of them - to go with race-neutral politics," said John Green, a professor of political science at the University of Akron in Ohio and a fellow at the Pew Forum on Religion & Public Life.

"Romney just danced around the issue. It was a complete nonstarter," Hollinger said. "He had the chance to really say something, but he didn't."

Still, a Gallup Poll taken in the days after Romney's speech found that 80 percent of the respondents would vote for "a well-qualified person for president who happened to be Mormon" - but that number was virtually unchanged from a similar poll taken four months earlier. Romney bowed out of the race in February.

Eagleton's depression

Eagleton's mental illness disclosures might have gone over differently in a later era.

In 1972, Democratic nominee Sen. George McGovern hastily chose Eagleton as his running mate, a selection agreed to a half-hour before the deadline at the Democratic National Convention. When McGovern asked Eagleton if he had any problems "that were significant or worth discussing with me," Eagleton said no.

Two weeks later, with news outlets in hot pursuit of the story, the running mates held a news conference at McGovern's vacation retreat in South Dakota. Eagleton divulged that "on three occasions in my life, I have voluntarily gone into hospitals as result of nervous exhaustion and fatigue." He added that he had undergone electric-shock therapy for depression on two of those visits.

At the press conference, McGovern said he "wouldn't have hesitated one minute if I had known everything Sen. Eagleton told you today." He pledged to support Eagleton "1000 percent."

But while the disclosures prompted a brief public discussion of mental illness, culturally, the pre-Prozac nation hadn't yet developed the vocabulary to have a long conversation about the subject. Often, Eagleton's depression was referred to in the press as "a nervous condition."

Days after the South Dakota press conference, Eagleton described his illness in detail in San Francisco before a gathering of wealthy fundraisers. One asked if McGovern could lose the election in the time "it would take to educate the American public that mental illness could be treated and cured," according to an account in The Chronicle. Eagleton replied that he didn't have the statistics, "but I know it is a fact that millions of American have periods of depression - of having the blues, being down in the dumps."

Even McGovern wasn't sure how the public would react. He may have misjudged. A Time magazine poll taken at the time found that 77 percent of the respondents said "Eagleton's medical record would not affect their vote." Eagleton left the ticket 18 days after joining it.